1. Field of the Invention
The present invention relates to a control device and control method for a stepping motor, and an image forming apparatus used for transmitting the driving force in a copying machine, a printer, a facsimile, or the like.
2. Related Background Art
A stepping motor used in an image forming apparatus or the like is a motor for driving by supplying a predetermined excitation pattern to the motor driver so that the rotation can be controlled for a stepping angle corresponding to the supplied excitation pattern.
Conventionally, the above-mentioned excitation pattern of the stepping motor is generated from a control CPU or using a dedicated circuit. Moreover, since an inexpensive stepping motor comprises an A phase, an A* phase, a B phase and a B* phase, the number of supply pattern lines to the motor driver is commonly four. Therefore, in a circuit for generating the excitation pattern, in general a pattern generation block is constituted by the four lines for each unit.
Moreover, when a smooth operation is further required depending on an object to be driven, the stepping motor can be driven using a motor driver capable of achieving a complicated excitation control. Among the motor drivers capable of achieving the complicated operation, there are those which cannot transmit the complicated control information with the four excitation pattern lines, so that the stepping motor is driven using a large number of controlling lines of 6 lines, 8 lines, or the like.
When the excitation pattern is generated by the control CPU as mentioned above, generation of the excitation pattern of the stepping motor itself may be a large load, depending on the size of the control job for the device to be the object. Then, in order to alleviate the load on the software, it is necessary to generate the excitation pattern using a dedicated pattern generating circuit.
However, also as to the dedicated pattern generating circuit, a problem of the circuit size thereof exists. That is, the interface of the motor driver to be the object and the driving method therefor varies widely, so that even if the exciting method is the same two-phase excitation, the excitation pattern to be supplied may be different depending on the kind of the stepping motor driver to be the object. Moreover, as mentioned above, there are many motor drivers which cannot be driven correctly without use of 6 lines or 8 lines instead of 4 lines. Therefore, in order to correspond to various kinds of motor drivers, it is necessary to provide the driving circuits with interfaces for the various kinds of motor drivers, respectively. However, a problem is involved in that it may lead to enlargement of the circuit size and the cost increase.